1. Field of the Invention
The present invention relates to an optical scanner, and more particularly, to a reflective mechanism of an optical scanner for reflecting light transmitted through a document.
2. Description of the Prior Art
Optical scanners equipped with an upper light source for scanning transparent documents such as color transparencies are commonly seen in the market. Such scanner usually comprises a base housing with a transparent top, a scanning mechanism movably mounted within the base housing equipped with a light source for scanning an image-bearing document positioned on the transparent top from underside if the document is opaque, and an upper housing pivotally mounted on the base housing above the transparent top with a movable light source for emitting light to the document from its top side if the document is transparent.
One problem is found when scanning some semi-transparent papers such as tracing papers by using such scanner. If the document is scanned by using the light source in the base housing, a lot of light received by the document will transmit through the document instead of reflecting back to the scanning mechanism and thus greatly reduces the acceptability of the resulting image or even makes the scanning impossible. It is also improper to use the light source in the upper housing to emit light to the document because a semi-transparent document is not transparent enough to allow enough light to pass through. In such case a user must use the light source in the base housing and place an opaque panel such as a white plastic board or a white paper above the semi-transparent document in order to reflect the light transmitted through the document back to the scanning mechanism. But adding an opaque panel usually complicates the document scanning work. First of all, such opaque panels are not always available when scanning those semi-transparent documents. Second, adding an opaque panel usually requires extra document alignment works to make sure that the document covered under the opaque panel is correctly aligned.